1. Field of the Invention
The present invention relates to vented and unvented fireplaces. More particularly, the present invention relates to novel fireplaces that are operable in either vented and/or unvented modes of operation.
2. Description of the Prior Art
It is well known that unvented gas fireplaces and heaters are capable of killing the occupants of a house. The condition can be described as heating a house with the exhaust gas from an automobile or a gas stove.
When the combustion products of gas fireplaces are inefficient, an excess amount of carbon monoxide (CO) builds up which results in carbon monoxide poisoning that can result in death or permanent brain damage.
It has been proposed to provide efficient burning unvented fireplaces which create less CO in the combustion products. However, the problem still exists that some CO is produced and will continue to build inside the house as long as the unvented gas fireplace is operated. The situation is analogous to a well known gas stove which burns gasses with highly efficient blue flames yet are also well known to produce CO build up which results in brain damage and death of occupants of a house.
For the above reasons, the American National Standards Institute (ANSI) has required that all unvented fireplaces be provided with an oxygen depletion thermocouple actuated switch at or near the gas pilot or burners on unvented fireplaces. Such oxygen depletion sensors shut down the gas valve to the burner system, thus, requiring restart of the system. Such sensors are located in the fireplace at the pilot of the burner and can only detect the oxygen depletion situation of the air entering the combustion chamber.
While no standard has been adopted for the requirement of CO detectors, such detectors are available and operate independent of a unvented fireplace and are usually installed in some remote area away from the fireplace.
It would be much better to detect an oxygen depletion or CO condition before any human damage can possibly occur and shut down a fireplace burner system which is creating the problem. It would be better yet to sense the CO level of the hot air that is being supplied to the room being heated by an unvented fireplace and restrict the level of the CO to a safe level so that no build up of CO is possible in the area being heated.